Effect of Surface Geology on Seismic Motion:
Challenges of Applying Ground Motion Simulation
to Seismology and Earthquake Engineering

Editorial Board (June 2020)
Editor-in-Chief
Yasuo Ogawa, Tokyo Institute of Technology, Japan

Vice Editors-in-Chief
Masato Furuya, Hokkaido University, Japan
Solid Earth Science

Nozomu Nishitani, Nagoya University, Japan
Space Science

Editors
Valerio Acocella
Ryosuke Ando
Kimiyuki Asano
Joseph B.H. Baker
Nanan Balan
Paul Bedrosian
Stephan Buchert
Phil Cummins
Hao Dong
Aditya Gusman
Shin-Chan Han
James Hickey
Thomas Hobiger
Hauke Hussmann
Takeo Ito
Art Jolly
Shunichi Kamata

Tomokazu Kobayashi
Alexey Kuvshinov
Juanjo Ledo
Huixin Liu
Yohei Miyake
Haruhisa Nakamichi
Yasuhito Narita
Takuya Nishimura
Takaaki Noguchi
Masahito Nose
Makiko Ohtake
Keiji Ohtsuki
Kyoko Okino
Duggirala Pallamraju
Severine Rosat
Akinori Saito
Tatsuhiko Saito

David Shelly
Hisayoshi Shimizu
Hiroko Sugioka
Sunny TamYoshiyuki Tanaka
Yanbin Wang
Yih-Min Wu
Chuang Xuan
Takuji Yamada
Mare Yamamoto
Takahiro Yamamoto
Yuhji Yamamoto
Tadashi Yamasaki
Tatsuhiro Yokoyama
Kazunori Yoshizawa

Hiroo Kanamori
Jun'ichiro Kawaguchi
Takafumi Matsui
Hitoshi Mizutani

Toshitaka Tsuda
Zhongliang Wu
Kiyoshi Yomogida

Advisory Board
Benjamin Fong Chao
Bernard Chouet
Yoshimori Honkura
Toshihiko Iyemori

Journal Scope
Earth, Planets and Space (EPS) is the official journal of the Society of Geomagnetism and Earth, Planetary
and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan, The
Geodetic Society of Japan, and The Japanese Society for Planetary Sciences.
EPS is a peer-reviewed, open-access journal published under SpringerOpen. It is an international journal
covering scientific articles in the entire field of earth and planetary sciences, particularly geomagnetism,aeronomy, space science, seismology, volcanology, geodesy, and planetary science. EPS also welcomesarticles in new and interdisciplinary subjects, and technical reports on instrumentation and software.
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Earth, Planets and Space(2018) 70:178
Wen et al. Earth, Planets and Space
https://doi.org/10.1186/s40623-018-0937-yOpen Access

PREFACESpecial issue “Effect of surface geology
on seismic motion: challenges of applying
ground motion simulation to seismology
and earthquake engineering”
Kuo‑Liang Wen1, Pierre‑Yves Bard2, Francisco‑José Sánchez‑Sesma3, Sadanori Higashi4, Tomotaka Iwata5*
and Takuto Maeda6

special issue on ESG published in 1992 in the Journal of
Physics of the Earth (a journal which was merged with
EPS in 1998).
This new special issue is a compilation of 18 papers on
ESG research, including topics such as seismic groundmotion observation; analysis and interpretations, including nonlinear site response; utilization of microtremors;and development of simulation methodologies for strong
ground motion prediction.
Seismic observation analysis has always been a key
research topic of ESG. Uetake (2017) reports interesting behavior in long-period ground motion recordedin the Kanto area, Japan. He demonstrates that theobserved long-period ground motions significantly differed among several distant earthquakes, although they
had similar locations, sizes and mechanisms. He showsthat the details of the velocity structure in the earthquake source region were the cause of the observed large
waveform packet, demonstrating the importance of considering structural inhomogeneities in the source side
for long-period ground motion prediction. Bijukchhen
et al. (2017) use the observed strong ground motions in
the Kathmandu valley during the 2015 Gorkha mainshock and aftershocks, to derive a one-dimensional
velocity structure model beneath the observed stations
and to compare them with the theoretical earthquake
H/V ratios. A unique strong ground motion study was
conducted by Sbaa et al. (2017), who performed sixdegrees-of-freedom observations using translationaland rotational sensors at two nearby sites in Kefalonia
Island, Greece, located on rock and soft soil conditions,

In the past few decades, numerous studies on the modification of seismic ground motion by surface geology andsubsurface structures (Effects of Surface Geology on seismic motion, ESG) have been carried out for improving
both our understanding of strong ground motion characteristics during destructive earthquakes and our ability
to perform reliable ground motion predictions of future
events. This has been enabled by increasing amountsof strong motion data and computing power. Research
into the quantification of ESG, and accounting for thoseeffects in everyday design and engineering practice is a
key element in the mitigation of earthquake disasters,
which are still occurring all over the world.
ESG International Conferences have been held in 1992
(Odawara, Japan), 1998 (Yokohama, Japan), 2006 (Grenoble, France), 2011 (Santa Barbara, USA) and 2016 (Taipei,
Taiwan). This 5th International Conference on the Effectsof Surface Geology on seismic motions (ESG5) was successful in several respects. It gathered an important number of researchers, field engineers and graduate students
from all over the world. The ESG5 proceedings include alarge amount of significant information. In order to offer
the research community a collection of peer-reviewed
contributions, the ESG5 Organizing Committee arranged
for the publication of a special issue on recent advances
into ESG research in Earth, Planets and Space (EPS),a journal published by Springer. This follows the last*Correspondence: iwata@egmdpri01.dpri.kyoto‑u.ac.jp
5
Disaster Prevention Research Institute, Kyoto University, Uji, Japan
Full list of author information is available at the end of the article© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made.

1

Effect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering
Wen et al. Earth, Planets and Space(2018) 70:178

Page 2 of 3

of fundamental modes of Rayleigh and/or Love waves.
Kawase et al. (2018) use statistical analysis to compare
microtremor (M) and earthquake (E) H/V spectral ratiosfrom a large set of permanent strong ground motion
stations to derive simple, frequency-dependent correction factors to estimate EHVSR from easily obtainable
MHVSR and propose a relatively simple method for thederivation of 1D velocity profiles from corrected microtremor H/V ratios. Matsushima et al. (2017) observeda directional dependence of microtremor H/V at the
Onahama station, Fukushima, Japan. The directional
analysis of dense, single-point microtremor measurements allowed them to identify the presence of a shallow,
wedge-like lateral heterogeneity, parallel to the directionof the axis of the larger microtremor H/V amplitude, consistent with the strong motion observations. Meanwhile,
Wu et al. (2017) propose a simplified approach to invert
the 1D velocity structure directly from the microtremor
H/V ratio, on the basis of the locked mode (“cap-layer”)
approximation allowing the use of the residue theorem.
Asano et al. (2017) obtain long-period inter-station
Green’s function in the Osaka sedimentary basin, Japan,
using ambient noise (microtremor) cross-correlation
functions. The fairly good match with the simulated
inter-station Green’s functions based on the present
Osaka sedimentary basin model (Sekiguchi et al. 2016)shows the applicability of noise cross-correlation for
velocity model validation. Salameh et al. (2017) propose,using a case study from Beirut (Lebanon), the combination of microtremor observations at ground surface withthose within buildings, coupled with a background model
based on extensive site and building response calculations, to provide urban-scale damage estimates on thebasis of easily available dynamic parameters (soil andbuilding frequencies, H/V amplitude). Kleinbrod et al.
(2017) show the usefulness and repeatability of ambient
vibration on rock slopes to characterize unstable areasfrom the directional dependence and the amplitude of
the H/V spectral ratios.
Finally, in order to optimize the efficiency of groundmotion prediction equations and building code provisions, site characterization issues should be addressed
continuously. Derras et al. (2017) use the KiK-net data
to investigate the performance of several parameters assite condition “proxies” to reduce the aleatory variabilityof GMPEs and recommend the use of pairs of proxies.
They also identify significant site response nonlinearities
and discuss the ability of various site proxies and loading to account for them. The objective of Stambouli et al.
(2017) is similar, i.e., to identify optimal site condition
proxies, but their approach is based exclusively on 1D,
linear numerical simulations, together with the use ofa special kind of neural network to derive appropriate

respectively. They found that the dependence on site conditions is stronger for torsional motion (rotation aroundthe vertical axis) than for rocking motion (rotation
around horizontal axis), which they interpreted as beinga result of more energetic Love waves on soft site conditions compared to Rayleigh waves. Kagawa et al. (2017)
compare the observed ground motion variations in thesource region of the 2016 Central Tottori earthquake tothe map of predominant site period derived from dense
microtremor observations in the area. They show thatlarger peak ground accelerations correspond to shorter
predominant periods, and also report significant period
shifts at some intermediate period sites during the main
shock, which they interpret as being related to nonlinear
site response.
Effects of nonlinear site response and/or liquefaction significantly impact strong ground motion characteristics. Ren et al. (2017) quantify the amount ofsoil nonlinearity by using various indices based on thehorizontal-to-vertical spectral ratio applied to strong
ground motion records obtained during and after the2008 Wenchuan earthquake, China (Ms8.0), and investigate their correlation with loading or site parameters.
Similarly, Chen et al. (2017) analyze the amount of nonlinear site response in the (estimated) strong shaking
area in relation to the loading and site parameters forthe 2016 Meinong earthquake and propose a method toincorporate the resulting nonlinear frequency shifts inotherwise linear stochastic ground motion simulations.
Lu et al. (2017) investigate the degree of damage to
low-rise buildings as a result of soil liquefaction in the
superficial layer during the 2016 Meinong earthquake,
Taiwan, and emphasize some nonconservative limitations of existing methods, linked to poor accountingof the underlying site conditions. Dhakal et al. (2017)transpose these nonlinear site response estimates basedon H/V ratios to the ocean bottom seismogram sitesof the Sagami Bay K-NET, Japan. Their observations
show that the degree of nonlinearity is generally larger
at the OBS sites due to the smaller threshold motions
that cause a nonlinear site response, compared with theavailable data at land sites.
The use of microtremors has been a permanent feature of ESG studies for many decades. Recently, building
on advances in the methodology of seismic interferometry of ambient noise or microtremors, Sánchez-Sesma
et al. (2011) and Kawase et al. (2011) use the diffuse
field theory to propose new relationships between anunderground velocity model and microtremor H/V, orearthquake H/V, respectively. Sánchez-Sesma (2017)
investigate the nonuniqueness issue of 1D velocity model
inversions based on the H/V spectral ratio only, by
inverting jointly the H/V ratio and the dispersion curves2

Earth, Planets and SpaceWen et al. Earth, Planets and Space(2018) 70:178

Page 3 of 3

relationships between various site parameters and site
amplification functions.
This special issue presents a representative selectionof recent advancements in ESG studies, including topics such as strong motion observation, field investigationof microtremor and/or seismic ground motions, theiranalysis using a wide variety of processing and inversion techniques, and their interpretation and comparison
with forward simulation models. These studies reflect theongoing efforts to improve strong ground motion prediction for future earthquakes. We expect new challenges
and further advances of ESG studies that contribute to
the reduction in earthquake disasters all over the world.

and predicting nonlinear site response. Earth Planets Space 69:133. https://doi.org/10.1186/s40623‑017‑0718‑z
Dhakal YP, Aoi S, Kunugi T, Suzuki W, Kimura T (2017) Assessment of nonlin‑
ear site response at ocean bottom seismograph sites based on S‑wave
horizontal‑to‑vertical spectral ratios: a study at the Sagami Bay area K‑NET
sites in Japan. Earth Planets Space 69:29. https://doi.org/10.1186/s4062
3‑017‑0615‑5
Kagawa T, Noguchi T, Yoshida S, Yamamoto S (2017) Effect of the surface geol‑ogy on strong ground motions due to the 2016 Central Tottori Earth‑quake, Japan. Earth Planets Space 69:106. https://doi.org/10.1186/s4062
3‑017‑0689‑0
Kawase H, Sánchez‑Sesma FJ, Matsushima S (2011) The optimal use of horizontal‑
to‑vertical (H/V) spectral ratios of earthquake motions for velocity structure
inversions based on diffuse field theory for plane waves. Bull Seismol Soc
Am 101:2001–2014
Kawase H, Mori Y, Nagashima F (2018) Difference of horizontal‑to‑vertical spectral
ratios of observed earthquakes and microtremors and its application to
S‑wave velocity inversion based on the diffuse field concept. Earth Planets
Space 70:1. https://doi.org/10.1186/s40623‑017‑0766‑4
Kleinbrod U, Burjánek J, Fäh D (2017) On the seismic response of instable rockslopes based on ambient vibration recordings. Earth Planets Space 69:126.
https://doi.org/10.1186/s40623‑017‑0712‑5
Lu C‑C, Hwang J‑H, Hsu S‑Y (2017) The impact evaluation of soil liquefaction on
low‑rise building in the Meinong earthquake. Earth Planets Space 69:109.
https://doi.org/10.1186/s40623‑017‑0693‑4
Matsushima S, Kosaka H, Kawase H (2017) Directionally dependent horizontal‑
to‑vertical spectral ratios of microtremors at Onahama, Fukushima, Japan.
Earth Planets Space 69:96. https://doi.org/10.1186/s40623‑017‑0680‑9
Ren Y, Wen R, Yao X, Ji K (2017) Five parameters for the evaluation of the soil non‑linearity during the Ms8.0 Wenchuan Earthquake using the HVSR method.
Earth Planets Space 69:116. https://doi.org/10.1186/s40623‑017‑0702‑7
Salameh C, Bard P‑Y, Guillier B, Harb J, Cornou C, Gérard J, Almakari M (2017)
Using ambient vibration measurements for risk assessment at an urban
scale: from numerical proof of concept to Beirut case study (Lebanon). Earth
Planets Space 69:60. https://doi.org/10.1186/s40623‑017‑0641‑3
Sánchez‑Sesma FJ (2017) Modeling and inversion of the microtremor H/V
spectral ratio: physical basis behind the diffuse field approach. Earth Planets
Space 69:92. https://doi.org/10.1186/s40623‑017‑0667‑6
Sánchez‑Sesma FJ, Rodríguez M, Iturrarán‑Viveros U, Luzón F, Campillo M,
Margerin L, García‑Jerez A, Suarez M, Santoyo MA, Rodriguez‑Castellanos A(2011) Theory for microtremor H/V spectral ratio: application for a layered
medium. Geophys J Int 186:221–225
Sbaa S, Hollender F, Perron V, Imtiaz A, Bard P‑Y, Mariscal A, Cochard A, Dujardin
A (2017) Analysis of rotation sensor data from the SINAPS@ Kefalonia(Greece) post‑seismic experiment—link to surface geology and wavefieldcharacteristics. Earth Planets Space 69:124. https://doi.org/10.1186/s4062
3‑017‑0711‑6
Sekiguchi H, Asano K, Iwata T, Yoshimi M, Horikawa H, Saomoto H, Hayashida T(2016) Construction of 3D velocity structure model of Osaka sedimentarybasin. In: Proceedings of the 5th international symposium for effects ofsurface geology on seismic motion, Taipei, 15–17 August 2016
Stambouli AB, Zendagui D, Bard PY, Derras B (2017) Deriving amplification factors
from simple site parameters using generalized regression neural networks:
implications for relevant site proxies. Earth Planets Space 69:99. https://doi.
org/10.1186/s40623‑017‑0686‑3
Uetake T (2017) Effects of subsurface structures of source regions on long‑period
ground motions observed in the Tokyo Bay area, Japan. Earth Planets Space
69:71. https://doi.org/10.1186/s40623‑017‑0655‑x
Wu H, Masaki K, Irikura K, Sánchez‑Sesma FJ (2017) Application of a simplified
calculation for full‑wave microtremor H/V spectral ratio based on the
diffuse field approximation to identify underground velocity structures.
Earth Planets Space 69:162. https://doi.org/10.1186/s40623‑017‑0746‑8

Authors’ contributions
All authors of this article served as guest editors for this special issue. All
authors read and approved the final manuscript.
Author details
1
Department of Earth Sciences, National Central University, Chungli, Taiwan,
ROC. 2 ISTerre, IFSTTAR, CNRS, IRD, Bâtiment, OSUG C, Grenoble‑Alpes Uni‑
versity, Grenoble, France. 3 Instituto de Ingeniería CU, Universidad Nacional
Autónoma de México, Coyoacán, Mexico. 4 Central Research Institute for Elec‑tric Power Industry, Abiko, Japan. 5 Disaster Prevention Research Institute,
Kyoto University, Uji, Japan. 6 Graduate School of Science and Technology,
Hirosaki University, Hirosaki, Japan.
Acknowledgements
We express sincere thankfulness to the authors who contributed to thisspecial issue, and reviewers who evaluated the contributions and gave helpfulcomments and suggestions.
Competing interests
The authors declare that they have no competing interests.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims in pub‑lished maps and institutional affiliations.
Received: 3 October 2018 Accepted: 3 October 2018

References
Asano K, Iwata T, Sekiguchi H, Somei K, Miyakoshi K, Aoi S, Kunugi T (2017) Sur‑face wave group velocity in the Osaka sedimentary basin, Japan, estimatedusing ambient noise cross‑correlation functions. Earth Planets Space 69:108.
https://doi.org/10.1186/s40623‑017‑0694‑3
Bijukchhen SM, Takai N, Shigefuji M, Ichiyanagi M, Sasatani T, Sugimura Y (2017)
Estimation of 1‑D velocity models beneath strong‑motion observation sites
in the Kathmandu Valley using strong‑motion records from moderate‑sizedearthquakes. Earth Planets Space 69:97. https://doi.org/10.1186/s4062
3‑017‑0685‑4
Chen C‑T, Chang S‑C, Wen K‑L (2017) Stochastic ground motion simulation of the2016 Meinong, Taiwan earthquake. Earth Planets Space 69:62. https://doi.
org/10.1186/s40623‑017‑0645‑z
Derras B, Bard P‑Y, Cotton F (2017) VS30, slope, H800 and f0: performance of vari‑
ous site‑condition proxies in reducing ground‑motion aleatory variability

3Effect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering

FULL PAPER

Open AccessUsing ambient vibration measurements for risk assessment
at an urban scale: from numerical proof of concept
to Beirut case study (Lebanon)
Christelle Salameh*, Pierre-Yves Bard, Bertrand Guillier, Jacques Harb, Cécile Cornou,
Jocelyne Gérard and Michelle Almakari
Earth, Planets and Space 2017, 69:60 DOI:10.1186/s40623-017-0641-3
Received: 1 January 2017, Accepted: 12 April 2017, Published: 26 April 2017

Abstract
Post-seismic investigations repeatedly indicate that structures having frequencies close to foundation soil frequencies exhibit significantly
heavier damages (Caracas 1967; Mexico 1985; Pujili, Ecuador 1996; L’Aquila 2009). However, observations of modal frequencies of soils andbuildings in a region or within a current seismic risk analysis are not fully considered together, even when past earthquakes havedemonstrated that coinciding soil and building frequencies leads to greater damage. The present paper thus focuses on a comprehensive
numerical analysis to investigate the effect of coincidence between site and building frequencies. A total of 887 realistic soil profiles arecoupled with a set of 141 single-degree-of-freedom elastoplastic oscillators, and their combined (nonlinear) response is computed for bothlinear and nonlinear soil behaviors, for a large number (60) of synthetic input signals with various PGA levels and frequency contents. The
associated damage is quantified on the basis of the maximum displacement as compared to both yield and ultimate post-elastic
displacements, according to the RISK-UE project recommendations (Lagomarsino and Giovinazzi in Bull Earthq Eng 4(4):415–443, 2006), andcompared with the damage obtained in the case of a similar building located on rock. The correlation between this soil/rock damage
increment and a number of simplified mechanical and loading parameters is then analyzed using a V
Damageindex
neural network approach. The results emphasize the key role played by the building/soil frequency
ratio even when both soil and building behave nonlinearly; other important parameters are the
PGA level, the soil/rock velocity contrast and the building ductility. A numerical investigation basedon simulation of ambient noise for the whole set of 887 profiles also indicates that the amplitude of
H/V ratio may be considered as a satisfactory proxy for site amplification when applied tomeasurements at urban scale. A very easy implementation of this method, using ambient vibration
measurements both at ground level and within buildings, is illustrated with an example application
for the city of Beirut (Lebanon).

D4 Complete

1.5dy

0.5(dy+du)

Vy

4

du

D3 Extensive

3

0.7dy

D2 Moderate

2

D1 Slight

1

D0 No damage

Keywords: Spectral coincidence, Nonlinearity, Seismic damage, Microtremor, Beirut, Neural network

du

dy

d

0

Graphical abstract*Corresponding author: Christelle Salameh, christelle.salameh@univ‑grenoble‑alpes.fr

FULL PAPER

Open Access

Stochastic ground motion simulation of the 2016 Meinong,
Taiwan earthquake
Chun-Te Chen*, Shun-Chiang Chang and Kuo-Liang Wen
Earth, Planets and Space 2017, 69:62 DOI:10.1186/s40623-017-0645-z
Received: 21 January 2017, Accepted: 14 April 2017, Published: 2 May 2017

Abstract
We applied a stochastic method for the finite-fault modeling of strong ground motions to the 2016 Meinong, Taiwan earthquake.
Newly developed attenuation models in Southern Taiwan with the frequency-dependent Q = 86.4f 0.73 and the high-frequency
decay factor κ0 were used in the synthetic model. The horizontal-to-vertical spectral ratios (HVSR) were calculated from weak
motions and the Meinong mainshock and used for the site amplification correction of the synthetic waveforms produced by thestochastic ground motion simulation. Simulations incorporating the attenuation models and site correction improved theprediction of the S-wave envelope, duration, and peak ground acceleration (PGA). The nonlinear site response during the
Meinong mainshock was identified by the degree of nonlinear site response (DNL), which is a summation of HVSR differences
between weak motions and the Meinong mainshock as recorded by the Taiwan Strong Motion Instrument Program. The DNL
showed a positive correlation with ground motion intensity. The surface site conditions influenced DNL strength. The percentage
of PGA reduction calculated in this study can be an indicator of
the spatial distribution of the degree of nonlinear soil effects on
the Meinong earthquake in the time domain. Areas that hadhigh levels of PGA reduction overlap with areas that had highliquefaction potential. Based on the residual analysis, forward
directivity was identified in a 105° range in the northwestward
direction. The amplification of forward rupture directivity was
three times greater than the backward rupture directivity.

Keywords: Stochastic method, HVSR, Nonlinear site
response, Rupture directivity

Graphical abstract*Corresponding author: Chun-Te Chen, pokayoke69@gmail.com
4Earth, Planets and Space

FULL PAPER

Open AccessDirectionally dependent horizontal-to-vertical spectral
ratios of microtremors at Onahama, Fukushima, Japan
Shinichi Matsushima*, Hiroyuki Kosaka and Hiroshi Kawase
Earth, Planets and Space 2017, 69:96 DOI:10.1186/s40623-017-0680-9
Received: 28 February 2017, Accepted: 6 July 2017, Published: 13 July 2017

Abstract
As observational evidence of 3-D microtremor horizontal-to-vertical spectral ratios (MHVRs), previous studies have shown thata significant directional dependency is observed in and around Uji campus, Kyoto University, Japan. This directional
dependence is considered to be the result of 2-D basin structure. In this study, we observed microtremors around a strong
motion observation site of the Port and Harbor Research Institute in Onahama, Japan, and found that directional dependenceof MHVRs exists in some parts of the area around the site. The directional dependence is more apparent and has a higher
dominant frequency, at around 5 Hz, relative to those observed in Uji, at around 0.5 Hz. We defined a parameter γ, which werefer to as the “directionally dependent coefficient” to indicate the magnitude of difference between the two orthogonalcomponents which implies the directional dependence of the MHVRs. We rotated the axes and calculated γ for each angle andsearched for the orientation that gave the largest γ at a point. Points for which the axis with larger MHVR amplitude among
the two axes is oriented in the NS direction are aligned in the NS direction, while points for which the axis with larger MHVR
amplitude is oriented in the EW direction are aligned in the EW direction. The distribution of points with large γ formed a
T-shaped distribution. We calculated the analytical and numerical MHVRs in order to simulate the observed MHVRs andsucceeded in showing the existence of a narrow
1010
10
wedge. From these results, we conclude that a
E2
C3
F4
9
9
9
8
8
8
wedge-like lateral heterogeneity exists in the shallow
7
7
7
subsurface of the studied area, parallel to the
6
6
6
5
5
5
direction of the axis of the larger MHVR amplitude.
4
4
4
Numerical EW
Observed EW

Numerical NS
Observed NS

Numerical EW
Observed EW

Numerical NS
Observed NS

Numerical EW
Observed EW

HVR

Numerical NS
Observed NS

Keywords: Horizontal-to-vertical spectral ratio,

Directional dependency, Microtremor,
Lateral heterogeneity, Onahama

3
2
1
0

1

FREQ (Hz)

3
2
1
0

10

1

FREQ (Hz)

3
2
1
0

10

1

FREQ (Hz)10

Graphical abstract*Corresponding author: Shinichi Matsushima, matsushima@sds.dpri.kyoto-u.ac.jp

FULL PAPER

Open Access

Estimation of 1-D velocity models beneath strong-motion
observation sites in the Kathmandu Valley using strong-motion
records from moderate-sized earthquakes
Subeg M. Bijukchhen*, Nobuo Takai, Michiko Shigefuji, Masayoshi Ichiyanagi, Tsutomu Sasatani
and Yokito Sugimura
Earth, Planets and Space 2017, 69:97 DOI:10.1186/s40623-017-0685-4
Received: 27 February 2017, Accepted: 14 July 2017, Published: 24 July 2017

Abstract
The Himalayan collision zone experiences many seismic activities with large earthquakes occurring at certain time intervals. The damming of the
proto-Bagmati River as a result of rapid mountain-building processes created a lake in the Kathmandu Valley that eventually dried out, leaving thickunconsolidated lacustrine deposits. Previous studies have shown that the sediments are ~600 m thick in the center. A location in a seismically active
region, and the possible amplification of seismic waves due to thick sediments, have made Kathmandu Valley seismically vulnerable. It has suffereddevastation due to earthquakes several times in the past. The development of the Kathmandu Valley into the largest urban agglomerate in Nepal
has exposed a large population to seismic hazards. This vulnerability was apparent during the Gorkha Earthquake (Mw7.8) on April 25, 2015, whenthe main shock and ensuing aftershocks claimed more than 1700 lives and nearly 13% of buildings inside the valley were completely damaged.
Preparing safe and up-to-date building codes to reduce seismic risk requires a thorough study of ground motion amplification. Characterizing
subsurface velocity structure is a step toward achieving that goal. We used the records from an array of strong-motion accelerometers installed by
Hokkaido University and Tribhuvan University to construct 1-D velocity models of station sites by forward modeling of low-frequency S-waves.
Filtered records (0.1–0.5 Hz) from one of the accelerometers installed at a rock site duringa moderate-sized (mb4.9) earthquake on August 30, 2013, and three moderate-sized(Mw5.1, Mw5.1, and Mw5.5) aftershocks of the 2015 Gorkha Earthquake were used as
input motion for modeling of low-frequency S-waves. We consulted available geologicalmaps, cross-sections, and borehole data as the basis for initial models for the sedimentsites. This study shows that the basin has an undulating topography and sediment sites
have deposits of varying thicknesses, from 155 to 440 m. These models also show highvelocity contrast at the bedrock depth which results in significant wave amplification.
cm/s/s0.25
KTP−80.2km

cm/s/s0.25

Input motion

−0.25
0.85

−0.25
1.35

TVU−78.7km

Simulated

−0.85
0.85

−0.85
0.75

Kathmandu Valley

Simulated

PPR−76.30km

20
1−D Simulation (Transverse)
BPF (0.2−0.7 Hz)

KPN−75.8km

0.00

−1.25

−0.75
30

Time(s)40

2015/05/16 11:34
27.56N 84.07E 7.0km Mw5.5

20

1−D Simulation (Transverse)
BPF (0.2−0.7 Hz)

Graphical abstract*Corresponding author: Subeg M. Bijukchhen, subeg@eng.hokudai.ac.jp
5

Observed

0.00

−0.75
0.75

THM−70.1km

0.00

Keywords: 1-D simulation, Velocity model, Propagator matrix, Diffused field theory,

BKT−65.30km

RNB−75.80km

0.00

PTN−75.7km

0.00

−0.75
1.25

Input motion

0.00

Observed

0.00

−1.35
0.75

KTP−80.20km

0.00

0.00

30

40
Time(s)2015/05/16 11:34
27.56N 86.07E 7.0km Mw5.5

Effect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering

FULL PAPER

Open Access

Deriving amplification factors from simple site parameters
using generalized regression neural networks: implications
for relevant site proxies
Ahmed Boudghene Stambouli*, Djawad Zendagui, Pierre-Yves Bard and Boumédiène Derras
Earth, Planets and Space 2017, 69:99 DOI:10.1186/s40623-017-0686-3
Received: 28 November 2016, Accepted: 14 July 2017, Published: 24 July 2017

Abstract
Most modern seismic codes account for site effects using an amplification factor (AF) that modifies the rock acceleration response spectra in
relation to a “site condition proxy,” i.e., a parameter related to the velocity profile at the site under consideration. Therefore, for practical purposes,
it is interesting to identify the site parameters that best control the frequency-dependent shape of the AF. The goal of the present study is toprovide a quantitative assessment of the performance of various site condition proxies to predict the main AF features, including the often usedshort- and mid-period amplification factors, Fa and Fv, proposed by Borcherdt (in Earthq Spectra 10:617–653, 1994). In this context, the linear,viscoelastic responses of a set of 858 actual soil columns from Japan, the USA, and Europe are computed for a set of 14 real accelerograms withvarying frequency contents. The correlation between the corresponding site-specific average amplification
factors and several site proxies (considered alone or as multiple combinations) is analyzed using thegeneralized regression neural network (GRNN). The performance of each site proxy combination is assessed
through the variance reduction with respect to the initial amplification factor variability of the 858 profiles.
Both the whole period range and specific short- and mid-period ranges associated with the Borcherdt factors
Fa and Fv are considered. The actual amplification factor of an arbitrary soil profile is found to be satisfactorily
approximated with a limited number of site proxies (4–6). As the usual code practice implies a lower numberof site proxies (generally one, sometimes two), a sensitivity analysis is conducted to identify the “bestperforming” site parameters. The best one is the overall velocity contrast between underlying bedrock andminimum velocity in the soil column. Because these are the most difficult and expensive parameters tomeasure, especially for thick deposits, other more convenient parameters are preferred, especially the couple(Vs30, f0) that leads to a variance reduction in at least 60%. From a code perspective, equations and plots areprovided describing the dependence of the short- and mid-period amplification factors Fa and Fv on thesetwo parameters. The robustness of the results is analyzed by performing a similar analysis for two alternative
sets of velocity profiles, for which the bedrock velocity is constrained to have the same value for all velocity
profiles, which is not the case in the original set.

Keywords: 1D linear site response, Site proxies, Amplification factors, Neural network

Graphical abstract*Corresponding author: Ahmed Boudghene Stambouli, stambouli_ahmed@yahoo.fr

FULL PAPER

Open Access

Surface wave group velocity in the Osaka sedimentary basin, Japan,
estimated using ambient noise cross-correlation functionsadKimiyuki Asano*, Tomotaka Iwata, Haruko Sekiguchi, Kazuhiro Somei, Ken Miyakoshi, Shin Aoi
and Takashi Kunugi
Earth, Planets and Space 2017, 69:108 DOI:10.1186/s40623-017-0694-3
Received: 27 February 2017, Accepted: 31 July 2017, Published: 15 August 2017

Abstract
Inter-station cross-correlation functions estimated using continuous ambient noise or microtremor records were used to extract theseismic wave propagation characteristics of the Osaka sedimentary basin,a Japan. Temporary continuous observations were conducted atLove wave
15 sites in the Osaka basin between 2011 and 2013. The data were analyzed135.2°E
using135.4°E
seismic
interferometry. The target period range was
135.6°E
34.8°N
2–8 s. Cross-correlations between all of the possible station pairs were calculated and stacked to produce a year-long data set, andRayleigh wave signals in the vertical and radial components and Love wave signals in the transverse component were identified from theresults. Simulation of inter-station Green’s functions using the finite difference
method was conducted to check the performance of the
34.6°Ncurrent three-dimensional velocity structure model. The measured time lag between the observed and theoretical Green’s functions wasless than 2 s for most station pairs, which is less than the wave period of interest in the target frequency range. Group velocity
34.4°N
tomography was applied to group delay times estimated by
T = 7.3 s
T = 4.3 s
T = 2.8 s
a Love wave
means of multiple filter analysis. The estimated group135.2°E
135.4°E
135.6°E
b Rayleigh wave
velocities for longer periods of 5–8 s exhibited spatial
34.8°N
135.2°E
135.4°E
135.6°E
variation within the basin, which is consistent with the
34.8°N
bedrock depth distribution; however, the group velocities
for shorter periods of 2–3 s were almost constant over the
34.6°N
34.6°Nstudied area. The waveform and group velocity information
obtained by seismic interferometry analysis can be useful for
future reconstruction of a three-dimensional velocity
34.4°N
34.4°NT = 7.3 s
T = 5.9 sbce
T f= 7.3 s T = 4.3 s
T = 4.3Ts= 2.8 s
structure model in the Osaka basin.

Keywords: Osaka sedimentary basin, Velocity structureb Rayleigh wave

model, Seismic interferometry, Surface wave,
Group velocity

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6Group velocity (km/s)

135.2°E
135.4°E
Fig. 9 Love and Rayleigh wave group velocities along theray path of eachstation pair at135.6°E
periods of 7.3, 5.9, 4.3, and 2.8 s
34.8°N abstract
Graphical*Corresponding author: Kimiyuki Asano, k-asano@egmdpri01.dpri.kyoto-u.ac.jp
in the middle period range. One possible explanation for6

this discrepancy is that the accuracy of the velocity structure was insufficient owing to the limited 34.6°N
amount of information available for use in developing the present modelin that area. In addition, the actual bedrock depth might
be deeper than the present velocity structure model. The
observed period of the Airy phase, which shows the minimum group velocity, was approximately 34.4°N
4 s for the Lovewave in this cell; thus, the actual depth of the bedrock is
between 0.5 and 1.0 km. However, possible reasons thatFor future reconstruction of the three-dimensional
velocity structure model in the Osaka sedimentary basin,
utilization of waveform information from inter-station
Green’s functions through waveform modeling is a direct
and straightforward method because it can naturally
include three-dimensional effects on wave propagationsuch as ray bending, multipathing, mode conversion, andgeneration of basin edge-induced surface waves. NeverT =surface
7.3 s wave group velocity T= 5.9 s is alsotheless,
tomography
a useful tool for identifying area in which further effort

T = 4.3 s

Earth, Planets and Space

FULL PAPER

Open Access

The impact evaluation of soil liquefaction on low-risebuilding in the Meinong earthquake
Chih-Chieh Lu*, Jin-Hung Hwang and Shang-Yi Hsu
Earth, Planets and Space 2017, 69:109 DOI:10.1186/s40623-017-0693-4
Received: 20 February 2017, Accepted: 31 July 2017, Published: 15 August 2017

Abstract
This paper presents major preliminary observations on the liquefaction-induced damages in the Meinong earthquake (ML =6.4). The severe damages to buildings centered on Huian and Sanmin Streets in Tainan City where the places were reclaimed
fish or farm ponds with poor construction quality from many decades ago. To better understand the effect due to the soilliquefaction at these sites, the information provided by the in situ 13 Standard Penetration Test boreholes and 5 Cone
Penetration Test soundings accompanying with the PGAs derived from the near seismographs was used to conduct the soilliquefaction evaluation by the Seed method (Seed et al. in J Geotech Eng ASCE 111(12):1425–1445, 1985) when subject to the
Meinong earthquake. The liquefaction potential index (LPI) was thenevaluated accordingly. From the results, it was found that the estimateddamage severity was not consistent to the field conditions if the local site
effect was not taken into account. To better reflect the site response inSinshin District
such sites, the sites’ PGAs in the PGA contour map were multiplied by 1.5
Annan Districttimes to quantify the amplification effects due to the soft geologicalcondition. In addition, the PGAs based on other simple approaches were
evaluated as well for comparison. Besides, the effects of fines content andmagnitude scaling factor were also discussed in this paper. After that,several common simplified methods were also used to calculate the LPI
Legend/Scalewhen subject to the Meinong earthquake in order to evaluate theapplicability of these simplified methods.
Epicenter
SSH

0.233g

L2

L6

TAI1
0.151g

L1

L4

L3

L5

TAI

0.238gKeywords: Liquefaction, Building damage, Uncertainty, Meinong

Epicenter
CWB rapid
reporting station
Location of soilliquefaction

0

2.5

5km
Base map obtained by Google earth

earthquake

Fig. 1*Corresponding author: Chih-Chieh Lu, chchlu@ncree.narl.org.tw

FULL PAPER

Open AccessFive parameters for the evaluation of the soil nonlinearity
during the Ms8.0 Wenchuan Earthquake using the HVSR
methodYefei Ren, Ruizhi Wen*, Xinxin Yao and Kun Ji
Earth, Planets and Space 2017, 69:116 DOI:10.1186/s40623-017-0702-7
Received: 27 February 2017, Accepted: 8 August 2017, Published: 22 August 2017

Abstract
The consideration of soil nonlinearity is important for the accurate estimation of the site response. To evaluate the soil nonlinearity during the2008 Ms8.0 Wenchuan Earthquake, 33 strong-motion records obtained from the main shock and 890 records from 157 aftershocks were collected
for this study. The horizontal-to-vertical spectral ratio (HVSR) method was used to calculate five parameters: the ratio of predominant frequency(RFp), degree of nonlinearity (DNL), absolute degree of nonlinearity (ADNL), frequency of nonlinearity (fNL), and percentage of nonlinearity (PNL).
The purpose of this study was to evaluate the soil nonlinearity level of 33 strong-motion stations and to investigate the characteristics,
performance, and effective usage of these five parameters. Their correlations with the peak ground acceleration (PGA), peak ground velocity(PGV), average uppermost 30-m shear-wave velocity (VS30), and maximum amplitude of HVSR (Amax) were investigated. The results showed that all
five parameters correlate well with PGA and PGV. The DNL, ADNL, and PNL also show a goodcorrelation with Amax , which means that the degree of soil nonlinearity not only depends on the
ground-motion amplitude (e.g., PGA and PGV) but also on the site condition. The fNL correlates withPGA and PGV but shows no correlation with either Amax or VS30 , implying that the frequency width
affected by the soil nonlinearity predominantly depends on the ground-motion amplitude rather
than the site condition. At 16 of the 33 stations analyzed in this study, the site response showed
evident (i.e., strong and medium) nonlinearity during the main shock of the Wenchuan Earthquake,where the ground-motion level was almost beyond the threshold of PGA > 200 cm/s2 or PGV > 15cm/s. The site response showed weak and no nonlinearity at the other 14 and 3 stations. These results
also confirm that RFp , DNL, ADNL, and PNL are effective in identifying the soil nonlinearity behavior.
The identification results vary for different parameters because each parameter has individualfeatures. The performance of the PNL was better than that of DNL and ADNL in this case study. The
thresholds of ADNL and PNL are proposed to be 2.0 and 7%, respectively.
Keywords: Wenchuan Earthquake, Soil nonlinearity, Site response, HVSR method, DNL, PGA, PGV,
VS30
Graphical abstract
103˚E

104˚E

105˚E

106˚E

34˚N

62SHW

33˚N

51HSD

400

200

31˚N

51LXT

51XJD

51JYH

51MZQ

600

51LXS

51SFB

400

51JYC
51JYD

51CXQ

200
100

600

7

0

Nonlinearity level

200

Strong

51PJD

30˚N

51TQL
51LDL

Medium
Weak
None

51LDD

*Corresponding author: Ruizhi Wen, ruizhi@iem.ac.cn

300

31˚N

51PJW

102˚E

400

32˚N

51AXT

51WCW

51QLY

30˚N

600
500

51GYZ

51GYS

51HSL 51MXD

51MXT
51MXN
51LXM

700

33˚N

200

51SPA

32˚N

900
800

62WUD
51JZY
51JZG
51JZW
62WIX

51JZB

cm/s2

103˚E

104˚E

PGA

102˚E
34˚N

105˚E

106˚E

Effect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering

FULL PAPER

Open AccessAnalysis of rotation sensor data from the SINAPS@ Kefalonia(Greece) post-seismic experiment—link to surface geology
and wavefield characteristics
Sarah Sbaa, Fabrice Hollender*, Vincent Perron, Afifa Imtiaz, Pierre-Yves Bard, Armand Mariscal,
Alain Cochard and Alain Dujardin
Earth, Planets and Space 2017, 69:124 DOI:10.1186/s40623-017-0711-6
Received: 31 March 2017, Accepted: 28 August 2017, Published: 11 September 2017

Abstract
Although rotational seismology has progressed in recent decades, the links between rotational ground motion and site soil conditions arepoorly documented. New experiments were performed on Kefalonia Island (Greece) following two large earthquakes (MW = 6.0, MW = 5.9) inearly 2014 on two well-characterized sites (soft soil, VS30 ~ 250 m/s; rock, VS30 ~ 830 m/s, VS30 being harmonic average shear-wave velocity
between 0 and 30 m depth). These earthquakes led to large six-component (three translations and three rotations) datasets of hundreds ofwell-recorded events. The relationship between peak translational acceleration versus peak rotational velocity is found sensitive to the site
conditions mainly for the rotation around the vertical axis (torsion; dominated by Love waves): the stiffer the soil, the lower the torsion, for agiven level of translational acceleration. For rotation around the horizontal axes (rocking; dominated by Rayleigh waves), this acceleration/
rotation relationship exhibits much weaker differences between soft androck sites. Using only the rotation sensor, an estimate of the Love-toa 10
Kefalonia rock (this study)
Rayleigh energy ratios could be carried out and provided the same results
Kefalonia soft-soil (this study)
as previous studies that have analyzed the Love- and Rayleigh-wave energy
GVDA (Yin et al. 2016)10
proportions using data from translational arrays deployed at the same twosites. The coupling of translational and rotational measurements appears to
10
be useful, not only for direct applications of engineering seismology, butalso to investigate the composition of the wavefield, while avoiding
deployment of dense arrays. The availability of new, low-noise rotation
10
sensors that are easy to deploy in the field is of great interest and should
extend the use of rotation sensors and expand their possible applications.
10
-2

-3

-4

-5

-6

Keywords: Rotational seismology, Wavefield characteristics, VS30 , Siteeffects, Love wave, Rayleigh waveb

*Corresponding author: Fabrice Hollender, fabrice.hollender@cea.fr

Graphical abstract

10 -2

10 -3

10 -4

FULL PAPER

Open Access

10 -5

On the seismic response of instable rock slopes based on
ambient vibration recordings
10 -6
10 -3

10 -2

10 -1

10 0

10 1 10 -3

10 -2

10 -1

10 0

10 1

Ulrike Kleinbrod*, Jan Burjánek and Donat Fäh
Earth, Planets and Space 2017, 69:126 DOI:10.1186/s40623-017-0712-5
Received: 28 February 2017, Accepted: 31 August 2017, Published: 11 September 2017

Abstract
Rock slope failures can lead to huge human and economic loss depending on their size and exact location. Reasonable hazard
mitigation requires thorough understanding of the underlying slope driving mechanisms and its rock mass properties.
Measurements of seismic ambient vibrations could improve the characterization and detection of rock instabilities since there
is a link between seismic response and internal structure of the unstable rock mass. An unstable slope near the village Gondo
has been investigated. The unstable part shows strongly amplified
ground motion with respect to the stable part of the rock slope. The
amplification values reach maximum factors of 70. The seismic
response on the instable part is highly directional and polarized.
Re-measurements have been taken 1 year later showing exactly thesame results as the original measurements. Neither the amplified
frequencies nor the amplification values have changed. Therefore,
ambient vibration measurements are repeatable and stay the same,if the rock mass has not undergone any significant change instructure or volume, respectively. Additionally, four new points
have been measured during the re-measuring campaign in order tobetter map the border of the instability.

Keywords: Ambient vibrations, Instable rock slopes, Siteamplification

Graphical abstract*Corresponding author: Ulrike Kleinbrod, ulrike.kleinbrod@sed.ethz.ch
8

Earth, Planets and Space

FULL PAPER

Open Access

VS30 , slope, H800 and f0 : performance of various site-condition proxies
in reducing ground-motion aleatory variability andpredicting nonlinear site response
Boumédiène Derras*, Pierre-Yves Bard and Fabrice Cotton
Earth, Planets and Space 2017, 69:133 DOI:10.1186/s40623-017-0718-z
Received: 18 January 2017, Accepted: 11 September 2017, Published: 22 September 2017

Abstract
The aim of this paper is to investigate the ability of various site-condition proxies (SCPs) to
reduce ground-motion aleatory variability and evaluate how SCPs capture nonlinearity site
effects. The SCPs used here are time-averaged shear-wave velocity in the top 30 m (VS30), thetopographical slope (slope), the fundamental resonance frequency (f0) and the depth beyond
which Vs exceeds 800 m/s (H800). We considered first the performance of each SCP taken alone
and then the combined performance of the 6 SCP pairs [VS30–f0], [VS30–H800], [f0–slope], [H800–
slope], [VS30–slope] and [f0–H800]. This analysis is performed using a neural network approach
including a random effect applied on a KiK-net subset for derivation of ground-motion
prediction equations setting the relationship between various ground-motion parameterssuch as peak ground acceleration, peak ground velocity and pseudo-spectral acceleration PSA(T), and Mw, RJB, focal depth and SCPs. While the choice of SCP is found to have almost no
impact on the median ground-motion prediction, it does impact the level of aleatory
uncertainty. VS30 is found to perform the best of single proxies at short periods (T < 0.6 s), while
f0 and H800 perform better at longer periods; considering SCP pairs leads to significant
improvements, with particular emphasis on [VS30–H800] and [f0–slope] pairs. The results also
indicate significant nonlinearity on the site terms for soft sites and that the most relevantloading parameter for characterising nonlinear site response is the “stiff” spectral ordinate at
the considered period.

35

Variance reduction Rσ (%)

30
25

Vs30

Vs30 and f0

H800

f0 and Slopef0

Vs30 and H 800

Slope

H800 and Slopef0 and H800

20

Vs30 and Slope

Vs30 and f0 and H800

15

All site proxies

10
5
0

35

Variance reduction Rφ (%)

30
25
20
15
10
5
0

35

Variance reduction Rτ (%)

30
25
20
15
10
5
0

Keywords: Aleatory variability, Site-condition proxies, KiK-net, Neural networks, GMPE,

0.01

0.1

1

2

4

0.1

1

2

4

Period (s)Graphical abstract

Nonlinear site response*Corresponding author: Boumédiène Derras, b_derras@mail.univ‑tlemcen.dz

FULL PAPER

Open Access

Application of a simplified calculation for full-wave microtremor
H/V spectral ratio based on the diffuse field approximation
to identify underground velocity structures
Hao Wu*, Kazuaki Masaki, Kojiro Irikura and Francisco José Sánchez-Sesma
Earth, Planets and Space 2017, 69:162 DOI:10.1186/s40623-017-0746-8
Received: 21 December 2016, Accepted: 15 November 2017, Published: 4 December 2017

Abstract19Depth(m)*Corresponding author: Hao Wu, haowu@geor.or.jp

0.1

1

Period(sec)

10−1
0.01

10

0.1

1

Period(sec)100
InitialAll
Identified

1

10

10

1000

InitialAll
Identified

Vs(m/s)Observed
SWcap(Init)
SWcap(Iden)

0.32
0.12
10−1
0.01

10

1

100

100

1000

SWcap
FW(Ide100

Graphical abstractSZOH26cap

GIFH29cap

10

1000

101

Depth(m)Surface waves, Underground velocity structures

InitialAll
Identified
1000

0Depth(m)Keywords: Diffuse field approximation, Microtremor H/V spectral ratio, Full-wave,

100

H/V

H/V

0

10−1
0.01

10

1

H/V

1

GIFH28cap

1

Depth(m)Depth(m)Depth(m)Under the diffuse field approximation, the full-wave (FW) microtremor H/V spectral ratio (H/V) is modeled as the square root of theratio of the sum of imaginary parts of the Green’s function of the horizontal components to that of the vertical one. For a given
layered medium, the FW H/V can be well approximated with only surface waves (SW) H/V
TCGH16cap
KMMH03cap
1
1of the “cap-layered” medium which consists of the given layered medium and a new larger
velocity half-space (cap layer) at large depth. Because the contribution of surface waves canbe simply obtained by the residue theorem, the computation of SW H/V of cap-layered
10
10
medium is faster than that of FW H/V evaluated by discrete wavenumber method andcontour integration method. The simplified computation of SW H/V was then applied to100
100
identify the underground velocity structures at six KiK-net strong-motion stations. The
Initial
InitialAll
All
inverted underground velocity structures were used to evaluate FW H/Vs which wereIdentified
Identified
1000
1000
consistent with the SW H/Vs of corresponding cap-layered media. The previous study on
100
1000
100
1000
Vs(m/s)Vs(m/s)surface waves H/Vs proposed with the distributed surface sources assumption and a fixed
Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement
Observed
Observed
SWcap(Init)
SWcap(All)
SWcap(Init)
SWcap(All)with the SW H/Vs of our study. The consistency between observed and theoretical spectral
SWcap(Iden) FW(Iden)
SWcap(Iden) FW(Iden)
10
10
ratios, such as the earthquake motions of H/V spectral ratio and spectral ratio of horizontal
motions between surface and bottom of borehole, indicated that the underground10
10
velocity structures identified from SW H/V of cap-layered medium were well resolved by
0.25
0.33
the new method.
0.11
0.14

0.1

KMMH14cap

100

1000

1

Period(sec)InitialAll
Identified

Effect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering

FULL PAPER

Open Access

Difference of horizontal-to-vertical spectral ratios of observed
earthquakes and microtremors and its application to S-wave
velocity inversion based on the diffuse field concept
Hiroshi Kawase*, Yuta Mori and Fumiaki Nagashima
Earth, Planets and Space 2018, 70:1 DOI:10.1186/s40623-017-0766-4
Received: 28 February 2017, Accepted: 19 December 2017, Published: 2 January 2018

Abstract
We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after
Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a
recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs fromearthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors(MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR sharesimilarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because
microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions
mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here thespectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites
into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for fivecategories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found thatpEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional
S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code
to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer tothose by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular
except for the average operation in EMRs. Finally, we showed independent examples of data not used in
the EMR calculation, where better ground structures were successfully identified from pEHVRs again.
Thus we proposed here a simple empirical method to estimate S-wave velocity structures using singlestation microtremor records, which is the most cost-effective method to characterize the site effects.

Keywords: Site effect, Subsurface structure, Seismological bedrock, Horizontal-to-vertical ratio,
Hybrid heuristic search, S-wave, P-wave

Graphical abstract*Corresponding author: Hiroshi Kawase, kawase@zeisei.dpri.kyoto-u.ac.jp

LETTER

Open Access

Assessment of nonlinear site response at ocean bottom seismographsites based on S-wave horizontal-to-vertical spectral ratios:a study at the Sagami Bay area K-NET sites in Japan
Yadab P. Dhakal*, Shin Aoi, Takashi Kunugi, Wataru Suzuki and Takeshi Kimura
Earth, Planets and Space 2017, 69:29 DOI:10.1186/s40623-017-0615-5
Received: 3 October 2016, Accepted: 2 February 2017, Published: 8 February 2017

Abstract
We analyzed S-wave horizontal-to-vertical (S-H/V) spectral ratios at six ocean bottom seismograph (OBS) sites of K-NET
located in the Sagami Bay area of Japan for nonlinear site responses. The degree of nonlinearity was computed by comparing
the S-H/V spectral ratios for strong motions (PGA ≥ 20 cm/s2) with those for weak motions (PGA < 20 cm/s2). Our analyses,
which showed that the weak-motion S-H/V spectral ratios differ from site to site, indicate that the underlying site geology is
not uniform at the OBS sites. It was found that the threshold PGA causing a nonlinear site response is generally different fromsite to site. Recordings having horizontal PGAs greater than about 50–150 cm/s2 display clear signatures of nonlinear site
effects, i.e., the shift of predominant frequencies to lower ones and/or the decrease in high-frequency spectral ratios. We also
found that the degree of nonlinearity is generally larger at the OBS sites dueto the smaller threshold motions that cause a nonlinear site responsecompared with the available data at land sites. The above findings suggest
the possibility of a widespread nonlinear site response at the OBS sites foroffshore earthquakes with a large magnitude. However, frequencies lower
than about 2 Hz are not affected by the nonlinear site response in theanalyzed data ranges (PGA < 467 cm/s2). These results indicate the need for
careful utilization of recorded strong motions at OBS sites for applications
such as real-time ground motion predictions as front detections.

Keywords: Ocean bottom seismograph, Nonlinear site response,
Horizontal-to-vertical spectral ratio, Sagami Bay

Graphical abstract*Corresponding author: Yadab P. Dhakal, ydhakal@bosai.go.jp
10Earth, Planets and SpaceLETTER

Open Access

Effects of subsurface structures of source regions on
long-period ground motions observed in the Tokyo Bay
area, Japan
Tomiichi Uetake
Earth, Planets and Space 2017, 69:71 DOI:10.1186/s40623-017-0655-x
Received: 21 December 2016, Accepted: 16 May 2017, Published: 22 May 2017

Abstract
We compared the long-period ground motion observed in the Tokyo Bay area during two shallow M6.7 earthquakes that
occurred in northern Nagano Prefecture, Japan, on March 12, 2011, and November 22, 2014. The magnitudes, focal depths,
and source mechanisms of these events were almost identical, but their seismograms were quite different. Significant longperiod later arrivals with a predominant period of 5 s were recognized in the velocity traces of the 2011 event, but there wereno such remarkable later arrivals in the 2014 event traces. The ground motions at stations located outside the basin area werestudied as incident waves to the Kanto Basin. A large wave packet with a predominant period of 5 s was recognized in thevelocity traces of the 2011 event, but there was no significant wave packet in the 2014 event traces. Based on particle motion,
this wave packet was hypothesized to be a Rayleighwave. The source regions of the two events havequite different subsurface structures. The different
characteristics in long-period ground motion in theTokyo Bay area during the two events were due todifferent Rayleigh wave excitations in the source
regions.

Keywords: Long-period ground motion, Rayleighwave, Velocity structure, Source region,
Kanto Basin

Graphical abstract

Corresponding author: Tomiichi Uetake, uetake.tomiichi@tepco.co.jp

EXPRESS LETTER

Open Access

Modeling and inversion of the microtremor H/V spectral
ratio: physical basis behind the diffuse field approachFrancisco J. Sánchez-Sesma
Earth, Planets and Space 2017, 69:92 DOI:10.1186/s40623-017-0667-6
Received: 13 March 2017, Accepted: 5 June 2017, Published: 4 July 2017

Abstract
Microtremor H/V spectral ratio (MHVSR) has gained popularity to assess the dominant frequency of soil sites. It requires
measurement of ground motion due to seismic ambient noise at a site and a relatively simple processing. Theory asserts thatthe ensemble average of the autocorrelation of motion components belonging to a diffuse field at a given receiver gives the
directional energy densities (DEDs) which are proportional to the imaginary parts of the Green’s function components whenboth source and receiver are the same point and the directions of force and response coincide. Therefore, the MHVSR can bemodeled as the square root of 2 × ImG11/ImG33, where ImG11 and ImG33 are the imaginary parts of Green’s functions at the load
point for the horizontal (sub-index 1) and vertical (sub-index 3) components,
respectively. This connection has physical implications that emerge from theduality DED force and allows understanding the behavior of the MHVSR. For agiven model, the imaginary parts of the Green’s functions are integrals along aradial wavenumber. To deal with these integrals, we have used either the popular
discrete wavenumber method or the Cauchy’s residue theorem at the poles that
account for surface waves normal modes giving the contributions due to Rayleighand Love waves. For the retrieval of the velocity structure, one can minimize theweighted differences between observations and calculated values using thestrategy of an inversion scheme. In this research, we used simulated annealing but
other optimization techniques can be used as well. This last approach allows
computing separately the contributions of different wave types. An example ispresented for the mouth of Andarax River at Almería, Spain.

Keywords: Ambient seismic noise, Site effects, Diffuse fields, H/V spectral ratio
Corresponding author: Francisco J. Sánchez-Sesma, sesma@unam.mx
11

Graphical abstractEffect of Surface Geology on Seismic Motion: Challenges of Applying Ground Motion Simulation to Seismology and Earthquake Engineering

EXPRESS LETTER

Open Access

Effect of the surface geology on strong ground motions
due to the 2016 Central Tottori Earthquake, Japan
Takao Kagawa*, Tatsuya Noguchi, Shohei Yoshida and Shinji Yamamoto
Earth, Planets and Space 2017, 69:106 DOI:10.1186/s40623-017-0689-0
Received: 28 February 2017, Accepted: 31 July 2017, Published: 15 August 2017

Abstract
On October 21, 2016, an earthquake with Japan Meteorological Agency (JMA) magnitude 6.6 hit the central part of Tottori Prefecture, Japan.
This paper demonstrates two notable effects of the surface geology on strong ground motions due to the earthquake. One is a predominantperiod issue observed over a large area. A seismic intensity of 6 lower on the JMA scale was registered at three sites in the disaster area.
However, the peak ground acceleration ranged from 0.3 to 1.4 G at the three sites because of the varying peak periods of observed strong
ground motions. The spectral properties of the observations also reflect the damage around the sites. Three-component microtremors wereobserved in the area; the predominant ground period distributions based on horizontal to vertical spectral ratios were provided by theauthors. The peak periods of the strong motion records agree well with predominant periods estimated from microtremor observations at arather hard site; however, the predominant periods of the microtremors are slightly shorter than those of the main shock at the other two soft
sites. We checked the nonlinear effect at the sites by comparing the site responses
to small events and the main shock. The peak periods of the main shock were longer
than those of the weak motions at the sites. This phenomenon indicates a nonlinear
site effect due to large ground motions caused by the main shock. A horizontal
component of the accelerogram showed rather pulsating swings that indicate cyclic
mobility behavior, especially at a site close to a pond shore; ground subsidence of~20 cm was observed around the site. The peak periods of weak motions agree wellwith those of the microtremor observations. This implies an important issue that the
predominant periods estimated by microtremors are not sufficient to estimate theeffect of surface geology for disaster mitigation. We have to estimate thepredominant periods under large ground motions considering the nonlinear site
response of soft sediment sites.

Keywords: Strong ground motion, Ground predominant period, Microtremor
observation, H/V spectrum, Nonlinear effect*Corresponding author: Takao Kagawa, kagawa@cv.tottori-u.ac.jp

12Fig. 1

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Contents
Special issue “Effect of surface geology on seismic motion: challenges of applying ground motion simulation toseismology and earthquake engineering”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kuo-Liang Wen, Pierre-Yves Bard, Francisco-José Sánchez-Sesma, Sadanori Higashi,
Tomotaka Iwata and Takuto Maeda

Using ambient vibration measurements for risk assessment at an urban scale: from numerical proof of concept
to Beirut case study (Lebanon). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Christelle Salameh, Pierre-Yves Bard, Bertrand Guillier, Jacques Harb,
Cécile Cornou, Jocelyne Gérard and Michelle Almakari

Stochastic ground motion simulation of the 2016 Meinong, Taiwan earthquake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chun-Te Chen, Shun-Chiang Chang and Kuo-Liang Wen
Directionally dependent horizontal-to-vertical spectral ratios of microtremors at Onahama, Fukushima, Japan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shinichi Matsushima, Hiroyuki Kosaka and Hiroshi Kawase
Estimation of 1-D velocity models beneath strong-motion observation sites in the Kathmandu Valley using
strong-motion records from moderate-sized earthquakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subeg M. Bijukchhen, Nobuo Takai, Michiko Shigefuji, Masayoshi Ichiyanagi,
Tsutomu Sasatani and Yokito Sugimura

Deriving amplification factors from simple site parameters using generalized regression neural networks: implications
for relevant site proxies. . . . . . . . . . . . Ahmed Boudghene Stambouli, Djawad Zendagui, Pierre-Yves Bard and Boumédiène Derras
Surface wave group velocity in the Osaka sedimentary basin, Japan, estimated using ambient noise cross-correlation
functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kimiyuki Asano, Tomotaka Iwata, Haruko Sekiguchi, Kazuhiro Somei,
Ken Miyakoshi, Shin Aoi and Takashi Kunugi

The impact evaluation of soil liquefaction on low-rise building in the Meinong earthquake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chih-Chieh Lu, Jin-Hung Hwang and Shang-Yi Hsu
Five parameters for the evaluation of the soil nonlinearity during the Ms8.0 Wenchuan Earthquake using the HVSR
method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yefei Ren, Ruizhi Wen, Xinxin Yao and Kun Ji
Analysis of rotation sensor data from the SINAPS@ Kefalonia (Greece) post-seismic experiment—link to surface
geology and wavefield characteristics. . . . . . . . . . . . . Sarah Sbaa, Fabrice Hollender, Vincent Perron, Afifa Imtiaz, Pierre-Yves Bard,
Armand Mariscal, Alain Cochard and Alain Dujardin

On the seismic response of instable rock slopes based on ambient vibration recordings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ulrike Kleinbrod, Jan Burjánek and Donat Fäh
VS30 , slope, H800 and f0 : performance of various site-condition proxies in reducing ground-motion aleatory variability
and predicting nonlinear site response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Boumédiène Derras, Pierre-Yves Bard and Fabrice Cotton
Application of a simplified calculation for full-wave microtremor H/V spectral ratio based on the diffuse fieldapproximation to identify underground velocity structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hao Wu, Kazuaki Masaki, Kojiro Irikura and Francisco José Sánchez-Sesma
Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to
S-wave velocity inversion based on the diffuse field concept. . . . . . . . . . . . . Hiroshi Kawase, Yuta Mori and Fumiaki Nagashima
Assessment of nonlinear site response at ocean bottom seismograph sites based on S-wave horizontal-to-vertical
spectral ratios: a study at the Sagami Bay area K-NET sites in Japan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yadab P. Dhakal, Shin Aoi, Takashi Kunugi, Wataru Suzuki and Takeshi Kimura
Effects of subsurface structures of source regions on long-period ground motions observed in the Tokyo Bay area, Japan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tomiichi Uetake
Modeling and inversion of the microtremor H/V spectral ratio: physical basis behind the diffuse field approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Francisco J. Sánchez-Sesma
Effect of the surface geology on strong ground motions due to the 2016 Central Tottori Earthquake, Japan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Takao Kagawa, Tatsuya Noguchi, Shohei Yoshida and Shinji Yamamoto

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Cover image: Chen, C.-T. et al., Earth, Planets and Space 2017, 69:62 DOI:10.1186/s40623-017-0645-z